Nanocarbon-reinforced aluminium composite materials and method for manufacturing the same

ABSTRACT

A nanocarbon-reinforced aluminum composite material and a method of manufacturing the same are provided. The method of manufacturing a nanocarbon-reinforced aluminum composite material is characterized in that composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, is added to molten aluminum and then casting the molten aluminum with the added composite powder.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority to Korean Patent Application No. 10-2014-0044439, filed on Apr. 14, 2014, the entire contents of which is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present disclosure relates to a nanocarbon-reinforced aluminum composite material and a method of manufacturing the same. More particularly, the present disclosure relates to a nanocarbon-reinforced aluminum composite material, wherein the reaction between nanocarbon and liquid aluminum is controlled and the dispersibility of nanocarbon in aluminum is improved, and to a method of manufacturing the same.

BACKGROUND

A carbon nanotube is a tubular carbon nanomaterial having a diameter of several nanometers (nm) to several tens of nanometers (nm).

It is well known that a carbon nanotube has excellent mechanical properties, such as high strength, a high elastic modulus, low density, a high aspect ratio, etc. Therefore, research into the application of carbon nanotubes to structural materials, that is, reinforcing materials, such as polymer-metal matrix composite materials and the like, has been actively conducted.

In the manufacture of a carbon nanotube-metal nanocomposite material, a powder metallurgy process of mixing carbon nanotubes with metal powder to prepare carbon nanotube-metal composite powder and then sintering this composite powder is generally used. In the powder metallurgy process, carbon nanotubes are mixed with metal powder by ball milling or the like, and then the mixture is sintered.

However, carbon nanotubes are strongly agglomerated by the Van der Waals force acting therebetween, and thus it is very difficult to uniformly disperse them in a metal matrix material. Further, the difference in density between carbon nanotubes and a metal matrix material makes the dispersion of carbon nanotubes difficult.

Further, since the agglomerated carbon nanotubes are not easily sintered, the density is low, and the characteristics of a composite material are poor. Further, when carbon nanotubes are mixed with metal powder, such as titanium powder, and then sintered, carbide, such as titanium carbide (TiC), is produced, and thus excellent reinforcing effects attributable to original carbon nanotubes are not achieved.

In particular, when a nanocarbon-reinforced aluminum composite material is manufactured using carbon nanotubes by a casting process, there is a problem in that the production of carbide by the reaction of nanocarbon and liquid aluminum must be prevented. Therefore, a method of coating nanocarbon with metal or ceramic has been done in order to solve the above problem. However, this method is also problematic in that the nanocarbon is damaged by the reaction of a metal coating layer with aluminum, and in that the dispersibility of nanocarbon is low because the wettability of a ceramic coating layer to aluminum is low.

It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.

SUMMARY

Accordingly, the present disclosure has been devised to solve the above-mentioned problems. The present disclosure provides a nanocarbon-reinforced aluminum composite material, wherein the reaction between nanocarbon and liquid aluminum is controlled and the dispersibility of nanocarbon in aluminum is improved, and a method of manufacturing the same.

An aspect of the present disclosure provides a method of manufacturing a nanocarbon-reinforced aluminum composite material comprising adding composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, to molten aluminum and then casting the molten aluminum with the added composite powder.

The method may include the steps of: coating nanocarbon with ceramic; mixing the ceramic-coated nanocarbon with metal powder to prepare composite powder such that the ceramic-coated nanocarbon is surrounded by the metal powder; adding the composite powder to molten aluminum; and casting the molten aluminum with the added composite powder.

The nanocarbon may include at least one selected from the group consisting of carbon nanotubes, carbon nanofiber, and graphene. The ceramic may include at least one selected from the group consisting of oxide, carbide, nitride, and boride.

The metal powder may be aluminum or a metal alloyed with the aluminum or reacted with the aluminum to form an intermetallic compound.

The ceramic-coated nanocarbon may be mixed with the metal powder by ball milling such that the ceramic-coated nanocarbon is surrounded by the metal powder.

Another aspect of the present disclosure provides a nanocarbon-reinforced aluminum composite material, manufactured by adding composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, to molten aluminum and then casting the molten aluminum with the added composite powder.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic view showing a process of manufacturing a nanocarbon-reinforced aluminum composite material according to an embodiment of the present disclosure;

FIG. 2 is a photograph showing carbon nanotubes coated with titanium oxide (TiO₂).

FIG. 3 is a photograph showing a nanocarbon-reinforced aluminum composite material according to an embodiment of the present disclosure.

FIG. 4 is a photograph showing a nanocarbon-reinforced aluminum composite material of Comparative Example 1.

FIG. 5 is a photograph showing TiO₂-coated carbon nanotube-aluminum composite powder prepared by ball milling.

FIG. 6 is a graph showing a graphene coated with Al₂O₃.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the attached drawings.

As shown in FIG. 1, the method of manufacturing a nanocarbon-reinforced aluminum composite material according to the present invention is characterized in that composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, is added to molten aluminum and then the molten aluminum with the added composite powder is casted.

That is, ceramic applied on nanocarbon controls the reaction between liquid aluminum and the nanocarbon, and the metal powder improves the wettability of liquid aluminum, thereby improving both thermal stability and dispersibility of nanocarbon in molten aluminum.

Nanocarbon can greatly contribute to the realization of high-functionalization, weight reduction, and miniaturization in the fields of electric and electronic appliances, automobiles, and the like in combination with existing metal materials because it has high electrical conductivity, high thermal conductivity and excellent mechanical properties. Therefore, in the present invention, the above advantages are realized by surrounding ceramic-coated nanocarbon with metal powder to prepare composite powder, adding the composite powder to molten metal and then casting the molten metal added with the composite powder.

The method of manufacturing a nanocarbon-reinforced aluminum composite material can be embodied by the steps of: coating nanocarbon with ceramic; mixing the ceramic-coated nanocarbon with metal powder to prepare composite powder such that the ceramic-coated nanocarbon is surrounded by the metal powder; adding the composite powder to molten aluminum; and casting the molten aluminum added with the composite powder.

Nanocarbon includes at least one selected from the group consisting of carbon nanotubes, carbon nanofiber, and graphene. The ceramic includes at least one selected from among oxide, carbide, nitride, and boride. For example, nanocarbon may be coated with metal powder by applying metal particles, such as copper, nickel or the like, and heat-treating them under an oxygen atmosphere.

Besides copper and nickel, gold, silver, platinum, titanium, zinc, manganese, and gallium may be used as metal powder. Thickness of a ceramic coating layer may be adjusted in a range of 10 nm to 1 μm. Further, ceramic coating may be performed by various methods, such as electroless plating, sputtering, deposition, chemical vapor deposition, and the like.

The ceramic coating may be performed such that ceramic particles are uniformly distributed on the nanocarbon. This uniformly ceramic-coated nanocarbon is surrounded by metal powder to prepare composite powder.

The composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, is mixed with molten aluminum, and then this mixture is cast, to manufacture a nanocarbon-reinforced aluminum composite material.

The metal powder may be aluminum or a metal alloyed with the aluminum or reacted with the aluminum to form an intermetallic compound. The ceramic-coated nanocarbon may be mixed with the metal powder by ball milling.

Hereinafter, the present disclosure will be described in more detail with reference to the following Examples.

Example 1

In order to manufacture a nanocarbon-reinforced aluminum composite material of the present disclosure, carbon nanotubes (CNTs) were coated with TiO₂ using a sol-gel process (see FIG. 2).

40 g of carbon nanotubes coated with TiO₂ were mixed with 160 g of aluminum powder by ball milling under the following conditions, thereby preparing composite powder having a structure in which carbon nanotubes are embedded in aluminum powder (see FIG. 5).

Raw material of ball: ZrO₂

Size of ball: 5 mm

Weight ratio of ball to powder: 10:1

Milling rate: 600 rpm

Milling time: 2 hours

200 g of the prepared composite powder was added to 800 g of molten aluminum at 750° C., mechanically stirred, and then cast to manufacture a nanocarbon-reinforced aluminum composite material. The agglomeration of nanocarbons was not seen in the nanocarbon-reinforced aluminum composite material of Example 1 (see FIG. 3).

Example 2

A nanocarbon-reinforced aluminum composite material was manufactured in the same manner as in Example 1, after graphene was coated with Al₂O₃ using a sol-gel process.

As shown in FIG. 6, the agglomeration of nanocarbons was not seen in the nanocarbon-reinforced aluminum composite material of Example 2.

Comparative Example 1

A nanocarbon-reinforced aluminum composite material was manufactured in the same manner as in Example 1, except that carbon nanotubes coated with TiO₂ were used.

As shown in FIG. 4, it can be ascertained from the nanocarbon-reinforced aluminum composite material of Comparative Example 1 that carbon nanotubes coated with TiO₂ were not dispersed in molten aluminum by mechanical stirring because the wettability of these carbon nanotubes to aluminum is low, and that the agglomeration of nanocarbons was observed in the composite material of Comparative Example 1.

As described above, according to the method of manufacturing a nanocarbon-reinforced aluminum composite material of the present disclosure, ceramic-coated nanocarbon is mixed with metal powder to prepare composite powder, thus improving the dispersibility of nanocarbon in aluminum while controlling the reaction between nanocarbon and liquid aluminum.

The nanocarbon-reinforced aluminum composite material of the present disclosure is advantageous in that the reaction between nanocarbon and liquid aluminum can be controlled, and the dispersibility of nanocarbon in aluminum can be improved.

Although the preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims. 

What is claimed is:
 1. A method of manufacturing a nanocarbon-reinforced aluminum composite material, comprising: adding composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, to molten aluminum; and casting the molten aluminum with the added composite powder.
 2. The method of claim 1, further comprising steps of: prior to adding the composite powder to molten aluminum and casting the molten aluminum with the added composite powder, coating nanocarbon with ceramic; and mixing the ceramic-coated nanocarbon with metal powder to prepare the composite powder such that the ceramic-coated nanocarbon is surrounded by the metal powder.
 3. The method of claim 2, wherein the nanocarbon includes at least one selected from the group consisting of carbon nanotube, carbon nanofiber, and graphene; and the ceramic includes at least one selected from the group consisting of oxide, carbide, nitride, and boride.
 4. The method of claim 3, wherein the metal powder is aluminum or a metal alloyed with the aluminum or reacted with the aluminum to form an intermetallic compound.
 5. The method of claim 1, wherein the ceramic-coated nanocarbon is mixed with the metal powder by ball milling such that the ceramic-coated nanocarbon is surrounded by the metal powder.
 6. A nanocarbon-reinforced aluminum composite material, manufactured by adding composite powder, in which ceramic-coated nanocarbon is surrounded by metal powder, to molten aluminum, and then casting the molten aluminum with the added composite powder. 